Production of shaped metallic articles



latented Get. 18, 1932 human sraras earner eterna- LEO SCHLECHT, F LUDWIGSHAFEN-ON-THE-RHINE WALTER, SCHUBARDT, 0E MANNHEIM, AND FRANZ DUFTSCHHID, OF HEIDELBERG, GERHANY, ASSIGNOBS T@ I. G. FARBENINDUSTRIE AKTIENGESELLSCHAFT, OF FRANKFOBT-ON-THE-MAIH,

GERMANY PRODUCTION OF SHAPED METALLIC ARTICLES No Drawing. Application filed February 28, 1931, Serial No. 519,246, and in Germany march 5, 1980.

The present invention relates to the pro sinter mould, especially when this is construct duction of shaped articles from metal powders by sintering by the action of heat.

In the manufacture and production of shaped articles from metal powders by sintering by the action of heat it is difiicult, especially in the preparation of large shaped articles, to obtain faultless pieces of metal since the shrinkage taking place during the sintering readily leads to the formation of shrinkage cracks.

We have now found that the said formation of cracks is practically completely avoided by causing the powder to sinter by the action of heat in such a spatial position that the direction of the shaped article in which the shrinkage of the sinter mass is greatest is about vertical. According to this method homogeneous shaped metallic articles free from cracks are obtained even with very large sintered masses. .By the process according to the present invention even metal powders which evolve considerable amounts of gas when heated, as for example iron containing carbon and oxygen, and which therefore can only be sintered with dificulty into articles free from cracks, may be sintered together in a faultless manner even when the heating is carried out rapidly, which, if desired, may 39 be efi'ected in stages. Since with shaped articles the extension of which is difierent in different directions the shrinkage is greatest in the direction of the greatest longitudinal extension, the greatest longitudinal direction or one of the greatest longitudinal directions of the shaped article is arranged vertically during the sintering according to the present invention.

Moreover, the further advantage is obplace very uniformly throughout the whole mass, while when carrying out the sintering in any other spatial position a great part of the sintered mass lies for example on the bottom of the furnace which is usually cooler, so that the mass is heated non-uniformly or insuficiently. I

In order to avoid adhesion of the material to be sintered to the walls of the sinter mould it is advantageous to coat the interior of the meal or similar refractory materials from tained that the heating of the powder takes ed of metal, with a layer ofa substance which does not sinter or become sticky when heated, as for example graphite, alumina, chamotte which no undesirable constituents can pass into the metal.

The following example will further illustrate the nature of this invention, but the invention is not restricted to this example. The parts are by weight.

Ewample A mixture of 100 partsof iron owder containing 1.2 per cent of carbon an' 1.5 per cent of oxygen obtained by the thermal decomposition of iron carbonyl and 1 part of flaky ferric oxide obtained by burning iron can bony] is charged into a sheet iron mould having the dimensions 55 by 152 by 220 millimetres which has been painted on the inside with a chamotte powder paste rich in alumina. The filled sheet iron mould, open at the top, is arranged with the longest edge vertical, that is with the surface 55 by 152 millimetres horizontally disposed, in an electrically heat ed annealing furnace and heated to 1000 C. or three hours, whereby vigorous evolution of gas and shrinkage takes place. In this manner a sintered block of ahomogeneous nature, quite free from cracks, which block may be readily removed from the sheet mould and which by rolling may be worked up into a sheet metal free from objection, is obtained.

If the said mixture be sintered in the same manner but with the surface 152 by 220 horizontally disposed, a sintered mass is formed which is covered-with wide cracks, consists of several unshaped single particles and is unsuitable for further working up by rolling.

What we claim is:

1. In the production of shaped metallic articles by sintcring a metallic powdenby the action of heat, the step which comprises arranging the uncompressed metal powder to be sintered in such a spatial position that the direction of the shaped article in which the shrinkage during the sintering is greatest, is about vertical. Q

2. In the. production of shaped metallic 1 i 2 Lemma articles by sintering a. metallic powder by the action of heat, the step which comprises arranging the uncompressed metal powderto he smtered in such a spatial position that the greatest longitudinal direction of the shaped erticle is about vertical during the sintere 3. In the production of shaped iron articles by sintering iron powder by the action of heat, the step which comprises arranging the uncompressed metal powder to be sintered in such a spatial position that the greatest longitudinel direction of the shaped article is about vertical during the sinterin in testimony whereof we have ereunto set our hands LEO SCl-HJECHT. I WALTER. SCHUJBARDT. FRANZ DWTSCHMID. 

